Plasticizers are non-volatile liquid compounds that impart flexibility to polymers and increase their range of end applications. The majority of plasticizers are used in the utilization of polyvinylchloride (PVC). PVC, due to its unique combination of price, performance, and versatile use, is one of the oldest and widely used high volume plastics. The PVC products formulated with various additives, range from very rigid pipes and siding to flexible flooring, sheeting, and adhesives. The compounding of PVC includes multifunctional additives that modify the properties; in general the formulations contain the polymer (resin), thermal stabilizers, fillers, plasticizers, and other specific property enhancers such as fire resistant materials. Rigid PVC may contain low levels of plasticizer usually less than 20 phr (parts per hundred parts resin) and is primarily used for pipe work, ducts, and similar applications where structural rigidity and chemical resistance is required. Flexible PVC contains high concentrations of plasticizer (up to 100+ phr) and is useful for numerous applications such as films, sheeting, cable coverings, moldings, stationary products, toys, hoses, leather goods, clothing and various furnishings.
The dominant class of plasticizers used in the vinyl industry today is the petroleum-derived phthalates. These compounds are produced by reacting phthalic anhydride with two equivalents of alcohol to form a diester. The largest produced phthalate for the vinyl industry is dioctyl phthalate (DOP).
Materials derived from natural/renewable resources have been proposed as alternatives to phthalate plasticizers. One example is a fully acylated monoglyceride ester derived from hydrogenated castor oil described, e.g., in U.S. Pat. Nos. 6,734,241 and 6,949,597, and sold under the name “Soft-n-Safe” by Danisco. Other examples include epoxidized fatty acid esters derived from epoxidized oils, such as linseed and soybean, trans-esterified with various polyols, as described, e.g., in U.S. Pat. No. 6,797,753.
Another example, described in WO2009/033240, features a mixture of glycerol esters containing natural fatty acyl chains and short acetyl groups, along with fatty acid ethyl esters. It appears that the unsaturated fatty acids are not modified and there are no fatty acyl chain backbone modifications to increase the polarity. In yet another example, described in WO2012/036913, estolide fatty acid esters and their use as plasticizers are described. These esters lack epoxy groups.